1. Department of Physics, Key Laboratory of Artificial Structures and Quantum Control, Ministry of Education, State Key Laboratory for Metal Matrix Composites, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, P. R. China, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100080, People’s Republic of China, State Key Lab of Electronic Thin Films and Integrated Devices, University of Electronic Science and...